I noticed today that Ken-chan has a white line going down the front of his fins that come down on the bottom before his actual fins. ( I look at them and think the feelers of a catfish or something) and I was wondering If that was a sign or maturity. ( The lines are identical on both feelers)

Keep in mind that the 13 months I have had him, not once has Ken-chan attempted to make a bubble nest.

Should I be worried in this or is my son just an eunich?

The other question is, How does one tell the age on a betta fish? Do they have to be a certain age before they can mate and how does one know besides the bubble nests?

If you've had him for 18 months, and he was probably about 8 months old when you got him, he would be over 2 years old, definitely not in prime breeding age which may be why he never builds bubble nests. What is his tank setup? What do you feed him? The white does not look rough of cottony right?